McNair is a census-designated place located in the Oak Hill section of Fairfax County, Virginia, United States.

[5][6] As of the 2020 census (some information from the 2022 American Community Survey) there were 21,598 people, 9,673 housing units and 8,759 households residing in the CDP.

Of the residents, 2.8% had Italian ancestry, 56.9% spoke a language other than English at home, and 43.6% were born outside the United States, 30.1% of whom were naturalized citizens.

The Dulles Toll Road (Virginia State Route 267) forms the northern edge of the CDP, and Virginia State Route 28 (Sully Road) forms part of the western border.

Via the Dulles Toll Road and Interstate 66 it is 25 miles (40 km) east to downtown Washington, D.C.